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Experiments in Fluids

, Volume 49, Issue 5, pp 1039–1051 | Cite as

Tip gap height effects on the aerodynamic performance of a cavity squealer tip in a turbine cascade in comparison with plane tip results: part 1—tip gap flow structure

  • Sang Woo LeeEmail author
  • Seon Ung Kim
Research Article

Abstract

Tip gap height effects on the flow structure over a cavity squealer tip have been investigated in a linear turbine cascade for power generation, in comparison with the corresponding plane tip results. Oil film flow visualizations are conducted on the tip surface and casing wall for tip gap height-to-chord ratios of h/c = 1.0, 2.0, and 3.0%. The squealer tip has a recessed cavity enclosed by a full length squealer with its rim height-to-chord ratio of 5.51%. The results show that most of in-coming fluid entering the tip gap inlet for the cavity squealer tip is entrapped by the suction-side squealer rim, and the cavity fluid is discharged into the blade flow passage over the suction-side squealer rim in the region from the mid-chord to the trailing edge. Regardless of h/c, the cavity squealer tip makes the leakage flow zone narrower than the plane tip, and is superior to the plane tip in reducing the tip leakage mass flow rate. A qualitative flow model describing full flow features over the cavity squealer tip is suggested. In this flow model, the tip gap exit area is classified into four different regions, and the tip gap height effects on the discharge characteristics in each region are discussed in detail.

Keywords

Separation Bubble Leakage Flow Suction Surface Stagnation Line Cavity Floor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

b

Axial chord length

c

Chord length

cc

Total length of camber line

h

Tip gap height

hst

Squealer rim height

ls

Distance from the leading edge geometric stagnation point to the trailing edge center point along the suction-side tip edge line

p

Pitch of the cascade

Re

Reynolds number (U c/ν)

s

Span of the turbine blade

U

Inlet free-stream velocity

x,y,z

Cascade coordinates

xc

Curvilinear coordinate along the camber line from the leading edge geometric stagnation point

xs

Curvilinear coordinate along the suction-side tip edge line from the leading edge geometric stagnation point

yd

y-directional coordinate at x/b = 1.1, mm

Greek symbols

ν

Kinematic viscosity of air

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.School of Mechanical EngineeringKumoh National Institute of TechnologyGyeongbukRepublic of Korea

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